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Cycle

Cross Coupling, Spur Suppression and Noise Rejection

CDCE706

SCAS815A – OCTOBER 2005 – REVISED OCTOBER 2005

controlled edge with respect to a t(

Θ) mean in a random sample of cycles. Phase jitter, Time Interval Error (TIE),

or Wander are used in literature to describe long-term variation in frequency. As of ITU-T: G.810, wander is

defined as phase variation at rates less than 10 Hz while jitter is defined as phase variation greater than 10 Hz.

The measurement interval must be long enough to gain a meaningful result. Wander can be caused by

temperature drift, aging, supply voltage drift, etc.

Figure 23. Snapshot of Phase Jitter

Cross-Coupling in ICs occurs through interactions between several parts of the chip such as between output

stages, metal lines, bond wires, substrate, etc. The coupling can be capacitive, inductive and resistive (ohmic)

induced by output switching, leakage current, ground bouncing, power supply transients, etc.

The CDCE706 is designed in BiCMOS process technology incorporating silicon-germanium (SiGe) technology.

This process gives excellent performance in linearity, low power consumption, best-in-class noise performance

and very good isolation characteristic between the on-chip components.

The good isolation was a major criteria to use BiCMOS process as it minimizes the coupling effect. Even if all

three PLLs are active and all outputs are on, the noise suppression is clearly above 50 dB. Figure 24 and

Figure 25 show an example of noise coupling, spur-suppression, and power supply noise rejection of CDCE706.

Die respective measurement conditions are shown in Figure 24 and Figure 25.

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